Vertex’s VX-661 Cystic Fibrosis Drug Candidate Gets FDA Orphan Drug Status Ahead of New Clinical Trials

Vertex Pharmaceuticals continues to break new ground on developing treatments for the orphan disease cystic fibrosis. Most recently, Vertex received the FDA’s Orphan Drug Designation for its investigational drug VX-661.

Orphan drug designation was established in January 1983 as a result of the Orphan Drug Act in order to encourage pharmaceutical companies to develop drugs to treat rare diseases. Although orphan drugs must go through the same rigorous testing as other pharmaceuticals before they can be marketed, some statistical burdens are lessened because clinical trials simply cannot recruit enough patients for a standard clinical trial. In addition, because the patient populations in orphan diseases such as CF are so small, the Orphan Drug designation gives drug developers more financial incentives to work on therapies through funding channels, exclusivity in marketing an approved therapy, and other perks.

VX-661 is a promising agent for treating cystic fibrosis because it is a cystic fibrosis transmembrane conductance regulator (CFTR) corrector. Vertex is using VX-661 in a Phase 2 clinical trial to treat cystic fibrosis patients homozygous for the F508del CFTR mutation, the most common mutation that affects 40% of cystic fibrosis patients. Treatment groups include VX-661, Vertex’s ivacaftor (Kalydeco), placebo, and combinations of drugs.

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The primary outcome in recent trials tested the drug’s safety in terms of frequency of adverse events, vital signs, and standard clinical laboratory values. Additional secondary outcomes identify the efficacy of VX-661 in enhancing forced expiratory volume in one second (FEV1) and improving the respiratory domain of the Cystic Fibrosis Questionnaire-Revised, among others. For upcoming clinical trials of VX-661, there will be 21 study locations — some of which are actively recruiting — but only an estimated 60 patients are expected to enroll in the study, illustrating the orphan disease status of cystic fibrosis. The study is projected to be completse in December 2014.

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